Monitoring and water quality impacts of an herbicide treatment on an aquatic invasive plant in a drinking water reservoir

Effective treatment options are needed for the management of aquatic invasive species. An herbicide treatment was used to control an invasive aquatic plant, yellow floating heart (Nymphoides peltata) in a 3350-acre drinking water reservoir. The purpose of this research was to document the success of the treatment in an individual cove of the reservoir using in-situ sampling and reservoir-wide using remotely sensed Sentinel-2 satellite imagery. We also determined if the dying vegetation negatively impacted biological oxygen demand and dissolved oxygen concentrations in the cove. The aquatic herbicide ProcellaCORTM (active ingredient = florpyrauxifen-benzyl) was used to treat a 55-acre infestation of YFH at a rate of 3 Prescription Dose Units (PDU)/ac-ft by a certified applicator in July 2019. Total surface coverage of yellow floating heart in the reservoir was reduced by more than 90% within 15 days after the treatment, and to less than 3.0 acres within 50 days after the treatment. No blooming flowers were observed after treatment and the surface coverage was close to 0% within 17 days after treatment in the cove. The effect of the herbicide treatment also appeared to carry over into the following growing season as the total surface coverage of yellow floating heart in the reservoir was less than 8 acres one year after the treatment in July 2020. The herbicide treatment resulted in short term increases in biological oxygen demand and decreases in dissolved oxygen at some sites in the cove within 3?10 days after the treatment. Dissolved oxygen then increased and concentrations were greater 42 days after treatment than they were before the treatment. Our results show that ProcellaCORTM has the potential to control yellow floating heart infestations with relatively short-term negative impacts on dissolved oxygen concentrations. We also show that Sentinel-2 satellite imagery can be used to monitor the success of herbicide applications over large spatial and temporal scales that would not be possible from ground based monitoring alone.

Automated summary

The research successfully controlled the invasive yellow floating heart in the reservoir using herbicide treatment, significantly reducing its coverage area post-treatment. Short-term negative impacts on dissolved oxygen concentrations were observed in the cove following the treatment.